The present invention relates to a panoramic image preparing method and a three-dimensional laser scanner.
A three-dimensional laser scanner has been known as a surveying device for acquiring three-dimensional data (3D data) of an object to be measured in a short time.
The three-dimensional laser scanner is installed at a reference point, scans a measurement range or an object to be measured with a pulse laser beam, measures a distance for each pulse laser beam and acquires point-group data. In a case where the point-group data is to be acquired in a wide range, the three-dimensional laser scanner is installed at other reference points, the three-dimensional laser scanner acquires the point-group data for an adjacent measurement range and synthesizes the acquired point-group data so as to make the acquirement of the point-group data in a wide range possible.
Further, there is a three-dimensional laser scanner which comprises an image pickup device, acquires an image of the measurement range by the image pickup device, acquires color information (RGB) of a measuring point from the acquired image, attaches the color information to three-dimensional coordinate of the measuring point and applies the coloring to the image of the object to be measured drawn by the point-group data so that the image can be easily recognized.
In a case where the measurement range of the three-dimensional laser scanner is widened, the measurement range becomes larger than a photographing range of a single image pickup device and thus, the image corresponding to the measurement range becomes a panoramic image acquired by synthesizing partially acquired images. FIG. 8 illustrates an example of a relationship between a panoramic image 83 and a photographing range 84 of the single image pickup device and one section illustrated in FIG. 8 indicates the photographing range 84 of the single image pickup device and the illustrated panoramic image 83 is composed of vertically 5 by laterally 5 photographing ranges 84.
Conventionally, in a case where a panoramic image is to be acquired, contrast is adjusted at a center of the panoramic image. The contrast is set so that the contrast becomes optimal at a center the photographing range 84, and the photographing of the entire measurement range is performed with the set contrast. However, brightness is usually different depending on a direction of photographing and a photographing position, and if the contrast is adjusted at the center photographing range 84, the contrast no longer becomes optimal in a part, which is too bright, and in a part which is too dark as exemplified in FIG. 9.
Therefore, the color information of image data acquired by photographing with the contrast, which is not optimal, is attached with respect to the measuring point of the part, which is too bright or too dark. Thus, the colored image prepared by the acquired point-group data also reflects the contrast state of the image data.